Method of producing solid metal materials containing pre-tensioned silica



United States Patent 3,303,006 METHOD OF PRODUCING SOLID METAL MA- TERIALS CONTAINING PRE-TENSIONED SILICA John Godfrey Morley, Derby, and Basil Allister Proctor, Mickleover, Derby, England, assignors to Rolls-Royce Limited, a British company No Drawing. Filed Feb. 12, 1962, Ser. No. 172,752 Claims priority, application Great Britain, Feb. 11, 1961, 5,187 61 1 Claim. (Cl. 29194) This invention relates to material and has for its object the provision of means whereby the plastic creep deformation characteristics of a material are improved.

According to the present invention a plurality of nonmetallic fibres are embedded in a matrix material the said fibres being prestressed by tensile loads prior to their being embedded in the matrix or being fibres which are capable of becoming stressed by tensile loads caused by an application of strain and/or heat, whereby plastic creep deformation of the matrix material will be retarded by the fibres.

The matrix may be made from any convenient material such as aluminium or other metal. The use of the term metal is to be understood as incorporating sintered metal powders which incorporate a proportion of oxide. The fibres may comprise any non-metallic material such as an inorganic silica fibre or a silicate glass fibre.

In order that the invention can be clearly understood and readily carried into effect three alternative methods of producing a material in accordance with the invention will now be described, by way of example only.

In one method a plurality of silica fibres of approximately 5X10" ins. in diameter are held at each end in suitable clamping devices, and the clamping devices are moved relatively to each other to apply a predetermined tensile stress to the fibres, for example 100,000 lb./sq. inch.

The stress is maintained on the fibres and they are then inserted in a mould or other receptacle and aluminium or other metal poured into the mould to envelope the fibres. When the metal has solidified sufiiciently the tension applied to the fibers is released whereby the plastic creep deformation characteristics of the aluminium under high temperature conditions is improved beyond the characteristics of aluminium without the fibres, by the compressive force applied thereto by the fibres.

In an alternative method of producing a material in accordance with the invention the fibre and matrix forming materials are chosen so that there is a large difference in their thermal expansion rates, whereby the fibres will be 3,303,006 Patented Feb. 7, 1967 ice placed under tensile stresses when the material is subjected to high temperatures, for example the fibres may have a thermal expansion rate of 5 X 10 C. whilst the matrix material may have a thermal expansion rate of 1x 10 C.

In a further alternative method the fibres and matrix are produced as in the first described method, but without any tensile stress being applied to the fibres, and then the material is subjected to a stress which is sufficient to cause plastic flow or creep of the metal, whereby the fibres have a tensile load applied to them.

The plastic deformation of the metal causes a re-distribution of stress in the system, the major portion of the load being borne by the fibres and transmitted to them by shear loads through the metal which shear loads may be arranged to be very small.

In each of the foregoing examples the fibre and matrix material have been chosen so that they both have substantially the same modulus of elasticity, but the two materials may be chosen so as to have widely differing moduli.

It will be appreciated that by employing a material in accordance with the invention excess creep tendencies in the material forming the matrix are avoided as would be the case if the stressed fibres were not employed.

What we claim is:

The method which comprises teusioning silica fibers maintained so that their longitudinal axes are substantially parallel to each other, enveloping the thus stressed fibers with a molten metal having creep characteristics and substantially the same modulus of elasticity as the fibers, allowing said metal to solidify and then releasing the tension on said fibers.

References Cited by the Examiner UNITED STATES PATENTS 2,143,016 1/1939 Kleinschmidt 527 2,328,302 8/1943 Simison 55527 2,609,320 9/1952 Modigliani 55527 2,616,165 11/1952 Brennan 29-183 2,699,415 1/1955 Nachtman 29452 2,737,802 3/1956 Bakker 29452 2,758,952 8/1956 Toulmin 29--l83 3,007,223 11/1961 Wehrmann 29452 3,098,723 7/1963 Micks 29183.5

DAVID L. RECK, Primary Examiner.

HYLAND BIZOT, Examiner.

N. F. MARKVA, Assistant Examiner. 

